mm/mremap.c

   1 /*
   2  *      mm/mremap.c
   3  *
   4  *      (C) Copyright 1996 Linus Torvalds
   5  *
   6  *      Address space accounting code   <alan@lxorguk.ukuu.org.uk>
   7  *      (C) Copyright 2002 Red Hat Inc, All Rights Reserved
   8  */
   9
  10 #include <linux/mm.h>
  11 #include <linux/hugetlb.h>
  12 #include <linux/shm.h>
  13 #include <linux/ksm.h>
  14 #include <linux/mman.h>
  15 #include <linux/swap.h>
  16 #include <linux/capability.h>
  17 #include <linux/fs.h>
  18 #include <linux/highmem.h>
  19 #include <linux/security.h>
  20 #include <linux/syscalls.h>
  21 #include <linux/mmu_notifier.h>
  22
  23 #include <asm/uaccess.h>
  24 #include <asm/cacheflush.h>
  25 #include <asm/tlbflush.h>
  26
  27 #include "internal.h"
  28
  29 static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr)
  30 {
  31         pgd_t *pgd;
  32         pud_t *pud;
  33         pmd_t *pmd;
  34
  35         pgd = pgd_offset(mm, addr);
  36         if (pgd_none_or_clear_bad(pgd))
  37                 return NULL;
  38
  39         pud = pud_offset(pgd, addr);
  40         if (pud_none_or_clear_bad(pud))
  41                 return NULL;
  42
  43         pmd = pmd_offset(pud, addr);
  44         split_huge_page_pmd(mm, pmd);
  45         if (pmd_none_or_clear_bad(pmd))
  46                 return NULL;
  47
  48         return pmd;
  49 }
  50
  51 static pmd_t *alloc_new_pmd(struct mm_struct *mm, struct vm_area_struct *vma,
  52                             unsigned long addr)
  53 {
  54         pgd_t *pgd;
  55         pud_t *pud;
  56         pmd_t *pmd;
  57
  58         pgd = pgd_offset(mm, addr);
  59         pud = pud_alloc(mm, pgd, addr);
  60         if (!pud)
  61                 return NULL;
  62
  63         pmd = pmd_alloc(mm, pud, addr);
  64         if (!pmd)
  65                 return NULL;
  66
  67         VM_BUG_ON(pmd_trans_huge(*pmd));
  68         if (pmd_none(*pmd) && __pte_alloc(mm, vma, pmd, addr))
  69                 return NULL;
  70
  71         return pmd;
  72 }
  73
  74 static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
  75                 unsigned long old_addr, unsigned long old_end,
  76                 struct vm_area_struct *new_vma, pmd_t *new_pmd,
  77                 unsigned long new_addr)
  78 {
  79         struct address_space *mapping = NULL;
  80         struct mm_struct *mm = vma->vm_mm;
  81         pte_t *old_pte, *new_pte, pte;
  82         spinlock_t *old_ptl, *new_ptl;
  83
  84         if (vma->vm_file) {
  85                 /*
  86                  * Subtle point from Rajesh Venkatasubramanian: before
  87                  * moving file-based ptes, we must lock truncate_pagecache
  88                  * out, since it might clean the dst vma before the src vma,
  89                  * and we propagate stale pages into the dst afterward.
  90                  */
  91                 mapping = vma->vm_file->f_mapping;
  92                 mutex_lock(&mapping->i_mmap_mutex);
  93         }
  94
  95         /*
  96          * We don't have to worry about the ordering of src and dst
  97          * pte locks because exclusive mmap_sem prevents deadlock.
  98          */
  99         old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl);
 100         new_pte = pte_offset_map(new_pmd, new_addr);
 101         new_ptl = pte_lockptr(mm, new_pmd);
 102         if (new_ptl != old_ptl)
 103                 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
 104         arch_enter_lazy_mmu_mode();
 105
 106         for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE,
 107                                    new_pte++, new_addr += PAGE_SIZE) {
 108                 if (pte_none(*old_pte))
 109                         continue;
 110                 pte = ptep_get_and_clear(mm, old_addr, old_pte);
 111                 pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr);
 112                 set_pte_at(mm, new_addr, new_pte, pte);
 113         }
 114
 115         arch_leave_lazy_mmu_mode();
 116         if (new_ptl != old_ptl)
 117                 spin_unlock(new_ptl);
 118         pte_unmap(new_pte - 1);
 119         pte_unmap_unlock(old_pte - 1, old_ptl);
 120         if (mapping)
 121                 mutex_unlock(&mapping->i_mmap_mutex);
 122 }
 123
 124 #define LATENCY_LIMIT   (64 * PAGE_SIZE)
 125
 126 unsigned long move_page_tables(struct vm_area_struct *vma,
 127                 unsigned long old_addr, struct vm_area_struct *new_vma,
 128                 unsigned long new_addr, unsigned long len)
 129 {
 130         unsigned long extent, next, old_end;
 131         pmd_t *old_pmd, *new_pmd;
 132         bool need_flush = false;
 133
 134         old_end = old_addr + len;
 135         flush_cache_range(vma, old_addr, old_end);
 136
 137         mmu_notifier_invalidate_range_start(vma->vm_mm, old_addr, old_end);
 138
 139         for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
 140                 cond_resched();
 141                 next = (old_addr + PMD_SIZE) & PMD_MASK;
 142                 /* even if next overflowed, extent below will be ok */
 143                 extent = next - old_addr;
 144                 if (extent > old_end - old_addr)
 145                         extent = old_end - old_addr;
 146                 old_pmd = get_old_pmd(vma->vm_mm, old_addr);
 147                 if (!old_pmd)
 148                         continue;
 149                 new_pmd = alloc_new_pmd(vma->vm_mm, vma, new_addr);
 150                 if (!new_pmd)
 151                         break;
 152                 next = (new_addr + PMD_SIZE) & PMD_MASK;
 153                 if (extent > next - new_addr)
 154                         extent = next - new_addr;
 155                 if (extent > LATENCY_LIMIT)
 156                         extent = LATENCY_LIMIT;
 157                 move_ptes(vma, old_pmd, old_addr, old_addr + extent,
 158                                 new_vma, new_pmd, new_addr);
 159                 need_flush = true;
 160         }
 161         if (likely(need_flush))
 162                 flush_tlb_range(vma, old_end-len, old_addr);
 163
 164         mmu_notifier_invalidate_range_end(vma->vm_mm, old_end-len, old_end);
 165
 166         return len + old_addr - old_end;        /* how much done */
 167 }
 168
 169 static unsigned long move_vma(struct vm_area_struct *vma,
 170                 unsigned long old_addr, unsigned long old_len,
 171                 unsigned long new_len, unsigned long new_addr)
 172 {
 173         struct mm_struct *mm = vma->vm_mm;
 174         struct vm_area_struct *new_vma;
 175         unsigned long vm_flags = vma->vm_flags;
 176         unsigned long new_pgoff;
 177         unsigned long moved_len;
 178         unsigned long excess = 0;
 179         unsigned long hiwater_vm;
 180         int split = 0;
 181         int err;
 182
 183         /*
 184          * We'd prefer to avoid failure later on in do_munmap:
 185          * which may split one vma into three before unmapping.
 186          */
 187         if (mm->map_count >= sysctl_max_map_count - 3)
 188                 return -ENOMEM;
 189
 190         /*
 191          * Advise KSM to break any KSM pages in the area to be moved:
 192          * it would be confusing if they were to turn up at the new
 193          * location, where they happen to coincide with different KSM
 194          * pages recently unmapped.  But leave vma->vm_flags as it was,
 195          * so KSM can come around to merge on vma and new_vma afterwards.
 196          */
 197         err = ksm_madvise(vma, old_addr, old_addr + old_len,
 198                                                 MADV_UNMERGEABLE, &vm_flags);
 199         if (err)
 200                 return err;
 201
 202         new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
 203         new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff);
 204         if (!new_vma)
 205                 return -ENOMEM;
 206
 207         moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len);
 208         if (moved_len < old_len) {
 209                 /*
 210                  * On error, move entries back from new area to old,
 211                  * which will succeed since page tables still there,
 212                  * and then proceed to unmap new area instead of old.
 213                  */
 214                 move_page_tables(new_vma, new_addr, vma, old_addr, moved_len);
 215                 vma = new_vma;
 216                 old_len = new_len;
 217                 old_addr = new_addr;
 218                 new_addr = -ENOMEM;
 219         }
 220
 221         /* Conceal VM_ACCOUNT so old reservation is not undone */
 222         if (vm_flags & VM_ACCOUNT) {
 223                 vma->vm_flags &= ~VM_ACCOUNT;
 224                 excess = vma->vm_end - vma->vm_start - old_len;
 225                 if (old_addr > vma->vm_start &&
 226                     old_addr + old_len < vma->vm_end)
 227                         split = 1;
 228         }
 229
 230         /*
 231          * If we failed to move page tables we still do total_vm increment
 232          * since do_munmap() will decrement it by old_len == new_len.
 233          *
 234          * Since total_vm is about to be raised artificially high for a
 235          * moment, we need to restore high watermark afterwards: if stats
 236          * are taken meanwhile, total_vm and hiwater_vm appear too high.
 237          * If this were a serious issue, we'd add a flag to do_munmap().
 238          */
 239         hiwater_vm = mm->hiwater_vm;
 240         mm->total_vm += new_len >> PAGE_SHIFT;
 241         vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT);
 242
 243         if (do_munmap(mm, old_addr, old_len) < 0) {
 244                 /* OOM: unable to split vma, just get accounts right */
 245                 vm_unacct_memory(excess >> PAGE_SHIFT);
 246                 excess = 0;
 247         }
 248         mm->hiwater_vm = hiwater_vm;
 249
 250         /* Restore VM_ACCOUNT if one or two pieces of vma left */
 251         if (excess) {
 252                 vma->vm_flags |= VM_ACCOUNT;
 253                 if (split)
 254                         vma->vm_next->vm_flags |= VM_ACCOUNT;
 255         }
 256
 257         if (vm_flags & VM_LOCKED) {
 258                 mm->locked_vm += new_len >> PAGE_SHIFT;
 259                 if (new_len > old_len)
 260                         mlock_vma_pages_range(new_vma, new_addr + old_len,
 261                                                        new_addr + new_len);
 262         }
 263
 264         return new_addr;
 265 }
 266
 267 static struct vm_area_struct *vma_to_resize(unsigned long addr,
 268         unsigned long old_len, unsigned long new_len, unsigned long *p)
 269 {
 270         struct mm_struct *mm = current->mm;
 271         struct vm_area_struct *vma = find_vma(mm, addr);
 272
 273         if (!vma || vma->vm_start > addr)
 274                 goto Efault;
 275
 276         if (is_vm_hugetlb_page(vma))
 277                 goto Einval;
 278
 279         /* We can't remap across vm area boundaries */
 280         if (old_len > vma->vm_end - addr)
 281                 goto Efault;
 282
 283         /* Need to be careful about a growing mapping */
 284         if (new_len > old_len) {
 285                 unsigned long pgoff;
 286
 287                 if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))
 288                         goto Efault;
 289                 pgoff = (addr - vma->vm_start) >> PAGE_SHIFT;
 290                 pgoff += vma->vm_pgoff;
 291                 if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
 292                         goto Einval;
 293         }
 294
 295         if (vma->vm_flags & VM_LOCKED) {
 296                 unsigned long locked, lock_limit;
 297                 locked = mm->locked_vm << PAGE_SHIFT;
 298                 lock_limit = rlimit(RLIMIT_MEMLOCK);
 299                 locked += new_len - old_len;
 300                 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
 301                         goto Eagain;
 302         }
 303
 304         if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT))
 305                 goto Enomem;
 306
 307         if (vma->vm_flags & VM_ACCOUNT) {
 308                 unsigned long charged = (new_len - old_len) >> PAGE_SHIFT;
 309                 if (security_vm_enough_memory(charged))
 310                         goto Efault;
 311                 *p = charged;
 312         }
 313
 314         return vma;
 315
 316 Efault: /* very odd choice for most of the cases, but... */
 317         return ERR_PTR(-EFAULT);
 318 Einval:
 319         return ERR_PTR(-EINVAL);
 320 Enomem:
 321         return ERR_PTR(-ENOMEM);
 322 Eagain:
 323         return ERR_PTR(-EAGAIN);
 324 }
 325
 326 static unsigned long mremap_to(unsigned long addr,
 327         unsigned long old_len, unsigned long new_addr,
 328         unsigned long new_len)
 329 {
 330         struct mm_struct *mm = current->mm;
 331         struct vm_area_struct *vma;
 332         unsigned long ret = -EINVAL;
 333         unsigned long charged = 0;
 334         unsigned long map_flags;
 335
 336         if (new_addr & ~PAGE_MASK)
 337                 goto out;
 338
 339         if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
 340                 goto out;
 341
 342         /* Check if the location we're moving into overlaps the
 343          * old location at all, and fail if it does.
 344          */
 345         if ((new_addr <= addr) && (new_addr+new_len) > addr)
 346                 goto out;
 347
 348         if ((addr <= new_addr) && (addr+old_len) > new_addr)
 349                 goto out;
 350
 351         ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1);
 352         if (ret)
 353                 goto out;
 354
 355         ret = do_munmap(mm, new_addr, new_len);
 356         if (ret)
 357                 goto out;
 358
 359         if (old_len >= new_len) {
 360                 ret = do_munmap(mm, addr+new_len, old_len - new_len);
 361                 if (ret && old_len != new_len)
 362                         goto out;
 363                 old_len = new_len;
 364         }
 365
 366         vma = vma_to_resize(addr, old_len, new_len, &charged);
 367         if (IS_ERR(vma)) {
 368                 ret = PTR_ERR(vma);
 369                 goto out;
 370         }
 371
 372         map_flags = MAP_FIXED;
 373         if (vma->vm_flags & VM_MAYSHARE)
 374                 map_flags |= MAP_SHARED;
 375
 376         ret = get_unmapped_area(vma->vm_file, new_addr, new_len, vma->vm_pgoff +
 377                                 ((addr - vma->vm_start) >> PAGE_SHIFT),
 378                                 map_flags);
 379         if (ret & ~PAGE_MASK)
 380                 goto out1;
 381
 382         ret = move_vma(vma, addr, old_len, new_len, new_addr);
 383         if (!(ret & ~PAGE_MASK))
 384                 goto out;
 385 out1:
 386         vm_unacct_memory(charged);
 387
 388 out:
 389         return ret;
 390 }
 391
 392 static int vma_expandable(struct vm_area_struct *vma, unsigned long delta)
 393 {
 394         unsigned long end = vma->vm_end + delta;
 395         if (end < vma->vm_end) /* overflow */
 396                 return 0;
 397         if (vma->vm_next && vma->vm_next->vm_start < end) /* intersection */
 398                 return 0;
 399         if (get_unmapped_area(NULL, vma->vm_start, end - vma->vm_start,
 400                               0, MAP_FIXED) & ~PAGE_MASK)
 401                 return 0;
 402         return 1;
 403 }
 404
 405 /*
 406  * Expand (or shrink) an existing mapping, potentially moving it at the
 407  * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
 408  *
 409  * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
 410  * This option implies MREMAP_MAYMOVE.
 411  */
 412 unsigned long do_mremap(unsigned long addr,
 413         unsigned long old_len, unsigned long new_len,
 414         unsigned long flags, unsigned long new_addr)
 415 {
 416         struct mm_struct *mm = current->mm;
 417         struct vm_area_struct *vma;
 418         unsigned long ret = -EINVAL;
 419         unsigned long charged = 0;
 420
 421         if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
 422                 goto out;
 423
 424         if (addr & ~PAGE_MASK)
 425                 goto out;
 426
 427         old_len = PAGE_ALIGN(old_len);
 428         new_len = PAGE_ALIGN(new_len);
 429
 430         /*
 431          * We allow a zero old-len as a special case
 432          * for DOS-emu "duplicate shm area" thing. But
 433          * a zero new-len is nonsensical.
 434          */
 435         if (!new_len)
 436                 goto out;
 437
 438         if (flags & MREMAP_FIXED) {
 439                 if (flags & MREMAP_MAYMOVE)
 440                         ret = mremap_to(addr, old_len, new_addr, new_len);
 441                 goto out;
 442         }
 443
 444         /*
 445          * Always allow a shrinking remap: that just unmaps
 446          * the unnecessary pages..
 447          * do_munmap does all the needed commit accounting
 448          */
 449         if (old_len >= new_len) {
 450                 ret = do_munmap(mm, addr+new_len, old_len - new_len);
 451                 if (ret && old_len != new_len)
 452                         goto out;
 453                 ret = addr;
 454                 goto out;
 455         }
 456
 457         /*
 458          * Ok, we need to grow..
 459          */
 460         vma = vma_to_resize(addr, old_len, new_len, &charged);
 461         if (IS_ERR(vma)) {
 462                 ret = PTR_ERR(vma);
 463                 goto out;
 464         }
 465
 466         /* old_len exactly to the end of the area..
 467          */
 468         if (old_len == vma->vm_end - addr) {
 469                 /* can we just expand the current mapping? */
 470                 if (vma_expandable(vma, new_len - old_len)) {
 471                         int pages = (new_len - old_len) >> PAGE_SHIFT;
 472
 473                         if (vma_adjust(vma, vma->vm_start, addr + new_len,
 474                                        vma->vm_pgoff, NULL)) {
 475                                 ret = -ENOMEM;
 476                                 goto out;
 477                         }
 478
 479                         mm->total_vm += pages;
 480                         vm_stat_account(mm, vma->vm_flags, vma->vm_file, pages);
 481                         if (vma->vm_flags & VM_LOCKED) {
 482                                 mm->locked_vm += pages;
 483                                 mlock_vma_pages_range(vma, addr + old_len,
 484                                                    addr + new_len);
 485                         }
 486                         ret = addr;
 487                         goto out;
 488                 }
 489         }
 490
 491         /*
 492          * We weren't able to just expand or shrink the area,
 493          * we need to create a new one and move it..
 494          */
 495         ret = -ENOMEM;
 496         if (flags & MREMAP_MAYMOVE) {
 497                 unsigned long map_flags = 0;
 498                 if (vma->vm_flags & VM_MAYSHARE)
 499                         map_flags |= MAP_SHARED;
 500
 501                 new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
 502                                         vma->vm_pgoff +
 503                                         ((addr - vma->vm_start) >> PAGE_SHIFT),
 504                                         map_flags);
 505                 if (new_addr & ~PAGE_MASK) {
 506                         ret = new_addr;
 507                         goto out;
 508                 }
 509
 510                 ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1);
 511                 if (ret)
 512                         goto out;
 513                 ret = move_vma(vma, addr, old_len, new_len, new_addr);
 514         }
 515 out:
 516         if (ret & ~PAGE_MASK)
 517                 vm_unacct_memory(charged);
 518         return ret;
 519 }
 520
 521 SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
 522                 unsigned long, new_len, unsigned long, flags,
 523                 unsigned long, new_addr)
 524 {
 525         unsigned long ret;
 526
 527         down_write(&current->mm->mmap_sem);
 528         ret = do_mremap(addr, old_len, new_len, flags, new_addr);
 529         up_write(&current->mm->mmap_sem);
 530         return ret;
 531 }